Database Reference
In-Depth Information
The increasing cost of protocol operations has been recognized by network
controller providers who, as one possible solution, provide ooad engines that
move the processing from the CPU to the network controller.
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4.4.4 Other Applications
Although not traditionally seen as high-performance data transport appli-
cations, interactive applications using video transmission over long-distance
networks have complex requirements regarding network transmission. Video-
conferencing applications
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require minimal latency in the video transmission
path. Using uncompressed or low-rate compressed video are options that can
be applied to videoconferencing. The data streams carrying uncompressed
video can use in excess of 1 Gbps transmission rates and are highly sensi-
tive to network latency and jitter. Fortunately, limited data loss is in some
cases considered acceptable for video streams because for interactivity it is less
costly to lose data than to retransmit it. Video transmission generally uses
the standard Realtime Transmission Protocol
*
on top of plain UDP. Video-
conferencing technology can be used for interactive remote visualization
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,
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as these two problems have similar challenges and requirements.
Another application is that of visualization of remote data. Often, scien-
tists need to locally visualize datasets generated on remote supercomputers
by scientific simulations. These datasets can be very large, and it is not de-
sirable to transfer the entire data file locally for visualization. As a user is
only interested in certain parts of the dataset at any given time, one al-
ternative is to transfer only the section(s) of interest to the local machine.
When the data is received, the visualization is updated and the user can
move to another section of interest.
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An important difference to file transfer
is that the user may access different sections of the data object, depending
on the type of data and analysis. The data transfer is not continuous. The
user may analyze a certain section for a while, then move on to the next
one. Data transfer is thus bursty, and a single data access may take as little
as one or two seconds as the application needs to remain responsive. This is
a significant difference to the file transfer scenario: for example, it is a ma-
jor issue for remote visualization (but not necessary for file transfer) if the
transport protocol takes several seconds to reach the maximum transfer rate.
One solution that is applicable to dedicated network connections are trans-
mission protocols with fixed data transmission rate. The data transmission
rate needs to be computed based on network, compute, and storage resource
availability.
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The destination of the transfer is the main memory of a local machine,
and network utilization can be improved by using remote main memory to
store (cached or prefetched) data of interest. We thus have disk-to-memory
*
http://www.faqs.org/rfcs/rfc3550.html. Accessed July 16, 2009.
